The funny thing about trying to apply this logic in reality is that it often breaks down in ways that can be really, really bad.

I've brought up this example many times before, but Measles is a great example. Measles resets your immune system and breaks immunological memory for anywhere up to three years after having recovered from it. But now we have a bunch of people that assume any diseases can simply be dealt with in a natural way by your immune system thanks to the logic above, and well, the consequences of that are becoming clear.